At one point, there was hope that one or two shots of a COVID vaccine would bring the pandemic to end, but over the past year, we’ve seen that the reality is far more complicated, as vaccine hesitancy slowed the rollout dramatically. Coupled with the spread of the highly contagious Delta variant and waning vaccine effectiveness, COVID is far from contained. As a result, the U.S. Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) recently approved amending the vaccine process to allow certain individuals in the U.S. to get a third vaccine shot. But there are multiple factors that might keep you from getting a booster right now.
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Overseas, a number of countries have been allowing people to mix and match their vaccines and boosters, getting a different vaccine for a third shot than the one they got initially. Thailand became one of the first countries to announce a mixed-vaccine regimen in July. And the U.K. is expected to push residents into getting a third booster dose that is different from their initial two shots, as research has shown that this might provide better protection against COVID, per the Financial Times.
But CDC Director Rochelle Walensky, MD, recently told Yahoo! Finance that there was not enough data in the U.S. to approve people mixing and matching vaccines here yet, despite the data from overseas.
“The FDA and the CDC advisory committees have reviewed the data—the efficacy data, the safety data, the waning data—for Pfizer and only Pfizer so far,” Walensky said previously, during a Sept. 24 White House press briefing. “The advice and recommendations we have given is for Pfizer boosts with people who received a Pfizer primary series.”
She told Yahoo! that information on mixing and matching vaccines is not far away. “We’re starting to see some of the mix-and-match data,” Walensky said, adding that studies on the matter are already under way.
The National Institute of Allergy and Infectious Diseases (NIAID) started a clinical trial with fully vaccinated adult volunteers in June to evaluate the safety and efficacy of receiving booster doses of different COVID vaccines. “The results of this trial are intended to inform public health policy decisions on the potential use of mixed vaccine schedules should booster doses be indicated,” NIAID Director Anthony Fauci, MD, said in a statement at the time.
Walensky added, “As soon as we have those data to present, both to the FDA and to the CDC, we’ll have recommendations there as well.”
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According to Yahoo!, the CDC’s Advisory Committee on Immunization Practices (ACIP) wanted to discuss mixing and matching when they met to analyze and vote on the Pfizer booster, but no vote has yet been scheduled for this regimen.
Some health experts appear frustrated with the CDC’s wait on approving a mixed vaccine process. Aaron Carroll, MD, a pediatrician and professor of pediatrics at Indiana University, told Yahoo! that allowing boosters from different vaccines is essentially no different from the flu shots people receive each year. “It’s not as if each year we authorize a brand of flu shot. This system is not built right,” Carroll explained.
Thomas Russo, MD, a professor and chief of infectious disease at the University of Buffalo’s Jacobs School of Medicine and Biomedical Sciences, also pointed out to VeryWell Health that during the initial vaccine rollout, some people mistakenly got Pfizer for their first shot and then Moderna for their second with no extreme effects.
“I don’t anticipate that there would be any issues from a safety point of view or an efficacy point of view in terms of crossing the two mRNA platforms,” Russo explained.
RELATED: Dr. Fauci Says Doing This Could “Defeat the Purpose” of Your Booster.